The invention relates to aqueous, coal dust suppression fluids, and formulations for the abatement of coal dust containing water dosed with dust suppression fluids. Furthermore, the invention relates to methods for the abatement of coal dust.
Dust suppression is the reduction of the extent to which finely divided solid particulate material becomes suspended in the air. A variety of materials such as coal, sulfur, phosphate, clay, and other finely divided ores and minerals, generate dust in transfer and handling operations during mining, transportation, storage, and use.
Dust is a particularly severe safety and health hazard in coal mining, handling, and storage operations. Coal often chips into small fragments by the action of wind and rain, frictional movement due to motion in transit, and abrasion in handling. Respirable coal dust has a particle size of less than about 10 microns and its inhalation can lead to pneumoconiosis, i.e., "black lung disease". Also, dust explosions due to spontaneous combustion may occur when the dust is confined to a small air space such as in coal mining operations.
It is known to suppress coal dust in mines by spraying with various aqueous systems containing chemical additives to improve working conditions and reduce the toxicological risks and explosion hazards. For example, U.S. Pat. No. 4,425,252 describes a method to abate coal dust using an anionic surfactant, preferably sodium dodecyclbenzene sulphonate and a nonionic surfactant, preferably a polyethoxylated nonylphenol, in an aqueous formulation. The method comprises spraying the coal dusty area with a formulation comprising water containing up to 0.1% by weight of the mixture of the anionic surfactant, i.e., a water soluble salt of an alkyl aryl sulfonic acid and nonionic surfactant having an HLB of from 10 to 16. Optimally, the mixture contains one or more cosolvents generally of the class of alkylene glycol monoalkyl ethers, C.sub.2 to C.sub.5 alkanols and mixtures thereof.
Furthermore, several techniques have been developed utilizing foamable compositions for suppressing coal dust. For example, U.S. Pat. No. 4,551,261 describes a foam comprising water, a foaming agent, and an elastomeric water insoluble polymer. A variety of anionic and nonionic surfactants and detergent wetting agents are described as useful foaming agents, and a variety of elastomeric and water insoluble synthetic organic polymer binders are described as useful elastomeric water insoluble polymers.
U.S. Pat. No. 4,971,720 describes a method for suppressing dust process emissions. The method utilizes a foaming agent which may be a low salt tolerant surfactant selected from salts of fatty acids, alkyl sulphates, and alkyl aryl sulphonates.
U.S. Pat. No. 4,561,905 describes a coal dust suppression mixture of oil, water and a surfactant in the form of an emulsion that is diluted and foamed. The foam is then sprayed into a falling mass of coal. The oils suitable for use are described as heavy process oils and include asphalt dissolved in a moderately heavy oil, residual flush oils or relatively high viscosity fuel oil. The preferred oils have a viscosity in the range of from approximately 600 to 7,000 SUS at 38.degree. C., a pour point in the range of approximately -18 to 21.degree. C., a molecular weight of at least 300 and a boiling point of at least 204.degree. C.
Thus, various techniques have been developed to suppress coal dust, and many of the techniques are effective for reducing that dust. However, there is still a need for improvement in coal dust suppression, and many of the prior techniques were developed without a need to address problems associated with modern coal mining practices.